Poultry is processed, after slaughtering, by scalding to assist in defeathering, defeathering by machine, washing, eviscerating and chilling prior to packing. These treatments are controlled to avoid causing a change in the appearance characteristics of poultry which would make it unsalable. Poultry, after eviscerating, shows high levels of salmonella bacteria on the surface of the carcass. A large part of carcass contamination with salmonella can be removed by water washing. While salmonella can be easily killed by heat, such as during cooking, colony forming units of bacteria can attach and/or reside in the regular and irregular surfaces of the skin, multiply and, thereafter, contaminate working surfaces, hands and utensils. Food spoilage and illness can result from this carry over of bacteria or cross-contamination from the infected carcass to surfaces not heated sufficiently to cause thermal destruction of the bacteria.
Extensive research has been conducted by the art to uncover an economical system for reducing salmonella contamination of poultry carcasses without causing organoleptic depredation. Poultry feathers carry large amounts of salmonella which can contaminate the carcass during scalding and defeathering. Improper evisceration can also be a source of contamination. The use of acids such as lactic or acetic acid, at levels sufficient to effect bacteriological control, causes organoleptic deterioration of the poultry. At acid levels low enough to avoid organoleptic deterioration of the poultry, bacteriostatic effects are reduced. A treatment system must be economical, easy to use, compatible with food manufacturing, and not change the organoleptic properties of the poultry. Any change in the appearance of the poultry would make the same unsalable.
It has been reported that the thermal death rate of salmonella can be increased during scalding by elevating the pH of the scald water to pH 9.0.+-.0.2. Agents such as sodium hydroxide, potassium hydroxide, sodium carbonate, and trisodium phosphate have been reported as effective pH adjusting agents for use in increasing the thermal death rate of the bacteria. Trisodium phosphate was reported as least effective in increasing the death rate. Sodium hydroxide and potassium hydroxide, while effective bacteriostats, can effect the surface of the carcass adversely. Propionic acid and glutaraldehyde, which were also tried as treating agents, are reported as possibly having unfavorable effects on plucking. See, "The Effect of pH Adjustment on the Microbiology of Chicken Scald-tank Water With Particular Reference to the Death Rate of Salmonella," T. J. Humphrey, et al., Journal of Applied Bacteriology, 1981, 51, pp. 517-527.
T. J. Humphrey, et al. have also reviewed the pH effect of scald water on salmonella on chicken skin. See "The Influence of Scald Water pH on the Death Rates of Salmonella typhimurium and Other Bacteria Attached to Chicken Skin," Journal of Applied Bacteriology, 1984, 57 (2), pp. 355-359. Scald water adjusted to pH 9.+-.0.2 as in the 1981 paper can help to reduce external and internal cross-contamination of carcasses by salmonellas.
The results reported in the first article are based on assays of samples of scald water taken from the scald tank. The article does not show the effect of the agents on bacterial colonies on the surface of the poultry or the organoleptic effect on the poultry meat or skin.
The second paper teaches that pH adjustment of scald water to pH of 9.+-.0.2 can be used to improve the hygiene of chicken carcasses during plucking by lowering the bacterial carry over from the scald tank.
These references are limited to the scald tank and use relatively low pH conditions and low concentration pH adjusting agents and do not show any long term effect of the agents on the surface of the poultry since the scald water solution and any agents therein are washed off after defeathering.
Humphrey, et al. recognize that plucking and subsequent evisceration cause further contamination. The improvements in scalding hygiene reported in their 1984 paper and in their earlier work 1981! help to reduce the growth rate of pathogens on carcass surfaces during plucking but have no measurable effect on the shelf-life or safety of chilled carcasses because of further contamination during evisceration. The organisms responsible for spoilage of meat of this type are added during cold storage or during later stages of processing. (Humphrey, et al. 1984 at page 359). Humphrey, et at. do not teach reducing the potential for salmonellosis by reducing the incidence and population of salmonella organisms. Humphrey, et al., 1984, also do not show the organoleptic effect of their treatment on the poultry carcasses, much of which is undesirable.
Attempts have been made to pasteurize poultry meat by treating the meat with a solution containing agents such as lactic acid, acetic acid, sodium carbonate, sodium borate, sodium chloride, potassium hydroxide, chlorine and EDTA. All treatments, except sodium borate, sodium chloride and sodium carbonate reduced the visual acceptability of the meat. Chlorine failed to destroy bacteria on the surface of the poultry but would be expected to control salmonella in water. See, Chemical Pasteurization of Poultry Meat, J. S. Teotia, Dissertation Abstracts Int'l. B., 1974, 34(a), 4142.
The following references treat various meat products to retain moisture, texture and tenderness. U.S. Pat. No. 3,782,975 to Zyss issued Jan. 1, 1974 teaches polyphosphate curing of fresh primal cuts of meat with a curing solution at pH 6 to 8, free of sodium, and containing about 1.0 to 20% by weight of a water soluble phosphate which can include orthophosphate.
U.S. Pat. No. 3,775,543 to Zyss issued Nov. 27, 1973 uses 0.2 to 20% by weight of a phosphate (which can be orthophosphate) treatment solution based on the ingredient mix of processed meat. The phosphate is used as a binding agent. Alkaline pH is found to decrease shelf-life. Salmonella is killed by cooking not by phosphate.
U.S. Pat. No. 3,493,392 to Swartz issued Feb. 3, 1970 pumps tuna with a phosphate treating solution including orthophosphate to improve yield of desired light flesh, to improve odor (less fishy) and to render the meat more tender and less dry. Pumping injects solution deep into the meat or fish and is not a surface treatment. Swartz uses mono and dialkali orthophosphate in Example IV and reports poor weight retention results compared to polyphosphates. U.S. Pat. No. 3,620,767 to Swartz issued Nov. 16, 1971 pumps bonito with a salt and phosphate including orthophosphate but no example is given. See also Canadian Patent 847,280 issued Jul. 21, 1970 to Swartz. These references employ polyphosphates for their water binding properties.
U.S. Pat. No. 2,770,548 teaches the anticaking properties of trialkali metal orthophosphates.
Trisodium phosphate has also been found to be effective in inhibiting the growth of blue mold in cuts and bruises in fruit by treating the broken surface with the solution of trisodium phosphate (U.S. Pat. No. 1,744,310).
Kohl, et al., U.S. Pat. No. 3,681,091, issued August 1, 1972, teaches treating foods including fish fillets with 10% solution of medium chain length polyphosphates.
Freund, et al., U.S. Pat. No. 2,957,770 teach improving the properties of meat with a composition which can include inorganic orthophosphates such as disodium hydrogen orthophosphate. Low concentrations of phosphate are employed.
Cheng, U.S. Pat. No. 4,683,139 issued Jul. 28, 1987 teaches a process for prepackaged fresh red meat at retail wherein the shelf-life of the meat is increased by treatment with an aqueous solution of an alkali metal salt or certain phosphate compounds, a reducing compound such as ascorbic acid and a sequestering or chelating agent such as citric acid. The phosphate can be an orthophosphate, pyrophosphate, tripolyphosphate and hexametaphosphate and will vary in the way the buffer solution is applied to the meat giving a pH below neutral. Szczesniak, et al., U.S. Pat. No. 4,075,357 issued Feb. 21, 1978, teaches salt combined with a secondary salt selected from alkali metal salts of organic acids and trisodium orthophosphate, polyphosphate, metaphosphate and ultraphosphate. Citrates are preferred combined with sodium chloride. These mixtures are used to control water activity in low moisture cooked food which have neutral pH.
U.S. Pat. No. 3,705,040 to Bynagte issued Dec. 5, 1972 teaches use of a solution of water, 2 to 3% acid pyrophosphates and 2 to 15% sodium phosphates including sodium orthophosphate to soak shrimp for at least two minutes followed by cooking for three minutes, cooling and peeling. The process improves the amount of shrimp meat recovered from the shell by reducing the strength of the under skin of the shrimp. Where sodium orthophosphate is employed in Example IV it is employed at 2%.
The preceding patents which pump or treat meat or fish with phosphates generally use needles to inject or mix into meat formulations a phosphate solution to bind water and improve texture of the product. Neutral pH formula are employed for these purposes. The patents do not teach the present invention of treating the surface of freshly slaughtered poultry with trialkali metal orthophosphate at pH 11.5 or greater to remove, reduce or retard bacterial contamination or growth on the poultry.
U.S. Pat. No. 4,592,892 to Ueno, et al. issued Jun. 3, 1986 teaches ethanol used to sterilize foods and machines can be enhanced by use of an aqueous solution of an alkali carbonate which may also contain a trialkali metal phosphate. Trialkali metal orthophosphate as well as sodium carbonate and other phosphates is used to treat a broth to reduce E. coli in Table 1. This patent fails to recognize that trisodium phosphate per se can remove, reduce or retard bacterial contamination on poultry. Orthophosphate is used only in combination with ethanol which is a popular disinfectant for machinery and food in Japan. Thomson, et at. "Phosphate and Heat Treatments to Control Salmonella and Reduce Spoilage and Rancidity on Broiler Carcasses," Poultry Science, 1979, pp. 139-143, treats poultry with 6% kena phosphate which is a polyphosphate blend of 90% sodium tripolyphosphate and 10% sodium hexametaphosphate. The phosphates did not significantly or consistently affect salmonella survival or total bacterial growth.
It is known that the shelf-life of chicken carcasses can be increased 1 to 2 days by chilling the poultry in a solution of 6% sodium tripolyphosphate/0.7% tetrasodium pyrophosphate (Kena-available from of Rhone-Poulenc Inc.). See, The Antimicrobial Effect Of Phosphate With Particular Reference To Food Products, L. L. Hargreaves, et al., The British Food Manufacturing Industries Research Association, Scientific and Technical Surveys, No. 76, April 1972, pp. 1-20 at page 12. Many patents and articles suggest the use of polyphosphates in preserving meat and fish products.
In addition, it is also stated in the Hargreaves reference at page 7 that G. Pacheco and V. M. Dias in an article entitled Bacteriolytic Action of Phosphates Mems Institute, Oswaldo Cruz, 52 (2), pp. 405-414, reported on the bacteriolytic action of solutions of monosodium, disodium, trisodium and dipotassium orthophosphates on dead and living cells of Salmonella typhosa, Escherichia coli and Staphylococcus aureus. Trisodium phosphate dodecahydrate is stated to have the greatest lytic action. This reference does not relate to treating poultry.
British Patent 935,413 teaches treating raw poultry in the chill tank with a non-cyclic polyphosphate. It is taught that this method provides increased preservation of the poultry flesh by decreasing exudate and thereby decreasing spread of bacteria.
U.S. Pat. No. 5,264,229 suggests shelf-life extension for commercially processed poultry by using a specialized hydrogen peroxide and a surfactant in the water used for chilling the poultry.
Commonly assigned U.S. Pat. Nos. 5,069,922, 5,143,260 and 5,283,073 are directed to a poultry carcass wash process which removes or reduces existing salmonella contamination as well as retards further contamination or growth without affecting the organoleptic properties of the poultry carcasses. While this technology has significantly has advanced the art, improvements can still be made in reducing the overall aerobic bacterial plate count, and thereby increasing the shelf-life of the poultry.